A brass instrument is sounded by buzzing the lips of the player against the mouthpiece, and the sounds produced therein are varied by manipulating the valve units. Namely, in the brass instrument is defined a column of air which is vibrated by buzzing the lips. The vibrating length of the column of air is directly related to the pitch of the sound produced, and the vibrating length is varied by manipulating one of the valve units.
A typical example of the brass instrument is shown in FIG. 1 in a modeled form, and largely comprises a funnel-shaped mouthpiece 1, a open-cone 3, a main tube member 5 interconnecting the mouthpiece 1 and the open cone 3, and three valve units 7, 9 and 11. The valve units 7, 9 and 11 are operative to couple bypassing tube members 13, 15 and 17 to the main tube member 5, respectively, thereby connecting additional lengths of tubing for the variation in the pitch of the sound produced therein.
The valve units are of the four-port rotary valve illustrated in FIG. 2 of the drawings. The valve units 7, 9 and 11 are similar in construction to one another, and, for this reason, description is made for the valve units 7 with reference to FIG. 2. The valve units 7 largely comprises a valve casing 19, a rotor 21 coupled to a key member 23. The valve casing 19 is provided with four ports 25, 27, 29 and 31, and two air conduits 33 and 35 are formed in the rotor 21. The rotor 21 is tightly received, but rotatable in the valve casing 19, and, for this reason, the air conduits 33 and 35 conduct the air without any serious leakage. Each of the air conduits 33 and 35 is bent at both end portions thereof, and one end portion of the air conduit 33 extends at right angles with one end portion of the air conduit 35.
The valve unit 7 is shiftable between first and second positions one of which allows the air conduit 33 to couple the port 27 to the port 29, and the other of which establishes an air passage from the port 27 through the air conduit 33, the bypassing air conduit 13, the port 31 and the air conduit 35 to the port 29. When the valve unit 7 remains in the first position, the air conduit 33 intervenes in the main tube member 5, and, accordingly, the column of air is relatively short. Then, if the player buzzes the lips, the relatively short column of air produces the vibration with a high pitch. In this situation, if the player manipulates the key member 23 to shift the valve unit 7 into the second position, the column of air is prolonged by the bypassing tube member 13, and, for this reason, the sound produced therein is lowered by a predetermined pitch.
However, a problem is encountered in the prior art brass instrument in that the player feels a difference in the air resistance depending upon the positions of the valve units 7, 9 and 11. This is because of the fact that each of the air conduits 33 and 35 are sharply bent in each rotor due to their being small in size, and, accordingly, the small radius of curvature imparts a substantial amount of resistance to the air passing therethrough. The difference in the air resistance is uncomfortable for the player and rather hard on the nerves. The variation in the air resistance further results in a difference in the tone color.